I have a team of 7 Human Resource members that I ran an experiment on using Experiment Wizard. I collect status on these 7 HRs as a group and get a result that is a collection of 4 states:
It makes sense with Idle and Busy if it would be 100%, but together with Travel Full and Travel to Work it does not make sense. Isn't traveling time also a busy time?
With the status busy is mend purely the time that the Human Resource is working at a server. The "travel time full" and "travel time empty" are indeed moments that the Human Resource is busy doing something (traveling), but the HR is not directly busy with the task at hand.
For many users it has an important added value to know how the time of a Human Resource is exactly spent (perhaps they have to redesign the production process by positioning 2 machines closer to each other to reduce travel time, or create teams with different skill sets). And exactly for that reason, the statuses have been split.